I would of course like to point out, he did not only speak against Christians - he also spoke to the violence done by fundamentalist Muslims, even fundamentalists Hindus in India during his time - - this quote just spoke of the Christians since in America that is most often who I tend to engage.
Change does not happen overnight, and it is not incumbent upon one man to change a system on his own - - the people as a whole must ultimately want to change the system and when they do - one man alone cannot stand in their way. Especially a system that was thousands of years old and would probably take a century or so to change. Even now, the Caste system is still prevalent in India - - more parts than others. I would imagine it will take quite a while for a system that has been there for thousands of years to be done away with .. though one could point out similar caste like systems in many societies so it is not Hindu or India specific.. but such is life.
Well if one speaks against the caste system.. and works for years to bring about an end to it - - first recognizing the untouchables as worthy of rights and of course was murdered before much of his goals could be achieved - - though at 78 who knows if he would have lived to completely revamp the system to a post Hindu Caste system.